Lithographic band gap tuning in photonic band gap crystals

We describe the lithographic control over the spectral response of three-dimensional photonic crystals. By precise microfabrication of the geometry using a reproducible and reliable procedure consisting of electron beam lithography followed by dry etching, we have shifted the conduction band of crystals within the near-infrared. Such microfabrication has enabled us to reproducibly define photonic crystals with lattice parameters ranging from 650 to 730 nm. In GaAs semiconductor wafers, these can serve as high-reflectivity (> 95%) mirrors. Here, we show the procedure used to generate these photonic crystals and describe the geometry dependence of their spectral response

The Pressure in 2, 2+1 and 3 Flavour QCD

We calculate the pressure in QCD with two and three light quarks on a lattice of size 16^3x4 using tree level improved gauge and fermion actions. We argue that for temperatures T > 2T_c systematic effects due to the finite lattice cut-off and non-vanishing quark masses are below 15% in this calculation and give an estimate for the continuum extrapolated pressure in QCD with massless quarks. We find that the flavour dependence of the pressure is dominated by that of the Stefan-Boltzmann constant. Furthermore we perform a calculation of the pressure using 2 light (m_u,d/T=0.4) and one heavier quark (m_s/T = 1). In this case the pressure is reduced relative to that of three flavour QCD. This effect is stronger than expected from the mass dependence of an ideal Fermi gas.Comment: 13 pages, LaTeX2

To what extent do the Classical Equations of Motion Determine the Quantization Scheme?

A simple example of one particle moving in a (1+1) space-time is considered. As an example we take the harmonic oscillator. We confirm the statement that the classical Equations of Motion do not determine at all the quantization scheme. To this aim we use two inequivalent Lagrange functions, yielding Euler-Lagrange Equations, having the same set of solutions. We present in detail the calculations of both cases to emphasize the differences occuring between them.Comment: LaTeX 20 page

Experimental studies of equilibrium vortex properties in a Bose-condensed gas

We characterize several equilibrium vortex effects in a rotating Bose-Einstein condensate. Specifically we attempt precision measurements of vortex lattice spacing and the vortex core size over a range of condensate densities and rotation rates. These measurements are supplemented by numerical simulations, and both experimental and numerical data are compared to theory predictions of Sheehy and Radzihovsky [17] (cond-mat/0402637) and Baym and Pethick [25] (cond-mat/0308325). Finally, we study the effect of the centrifugal weakening of the trapping spring constants on the critical temperature for quantum degeneracy and the effects of finite temperature on vortex contrast.Comment: Fixed minor notational inconsistencies in figures. 12 pages, 8 figure

Nonequilibrium effects of anisotropic compression applied to vortex lattices in Bose-Einstein condensates

We have studied the dynamics of large vortex lattices in a dilute-gas Bose-Einstein condensate. While undisturbed lattices have a regular hexagonal structure, large-amplitude quadrupolar shape oscillations of the condensate are shown to induce a wealth of nonequilibrium lattice dynamics. When exciting an m = -2 mode, we observe shifting of lattice planes, changes of lattice structure, and sheet-like structures in which individual vortices appear to have merged. Excitation of an m = +2 mode dissolves the regular lattice, leading to randomly arranged but still strictly parallel vortex lines.Comment: 5 pages, 6 figure